This invention relates to fuel compositions for internal combustion engines, and more particularly to fuel compositions containing ashless dispersants capable of reducing and/or preventing the deposit of solid materials in internal combustion engines and in particular in the intake systems and fuel port injector nozzles.
The prior art discloses many ashless dispersants useful as additives in fuels and lubricant compositions. A large number of such ashless dispersants are derivatives of high molecular weight carboxylic acid acylating agents. Typically, the acylating agents are prepared by reacting an olefin (e.g., a polyalkene such as polybutene) or a derivative thereof, containing for example at least about 10 aliphatic carbon atoms or generally at least 30 to 50 aliphatic carbon atoms, with an unsaturated carboxylic acid or derivative thereof such as acrylic acid, methylacrylate, maleic acid, fumaric acid and maleic anhydride. Dispersants are prepared from the high molecular weight carboxylic acid acylating agents by reaction with, for example, amines characterized by the presence within their structure of at least one N-H group, alcohols, reactive metal or reactive metal compounds, and combinations of the above. The prior art relative to the preparation of such carboxylic acid derivatives is summarized in U.S. Pat. No. 4,234,435.
It also has been suggested that the carboxylic acid derivative compositions such as those described above can be post-treated with various reagents to modify and improve the properties of the compositions. Acylated nitrogen compositions prepared by reacting the acylating reagents described above with an amine can be post-treated, for example, by contacting the acylated nitrogen compositions thus formed with one or more post-treating reagents selected from the group consisting of boron oxide, boron oxide hydrate, boron halides, boron acids, esters of boron acid, carbon disulfide, sulfur, sulfur chlorides, alkenyl cyanides, carboxylic acid acylating agents, aldehydes, ketones, phosphoric acid, epoxides, etc. Lists of the prior art relating to post-treatment of carboxylic ester and amine dispersants with reagents such as those described above are contained in a variety of patents such as U.S. Pat. No. 4,203,855 (Col. 19, lines 16-34) and U.S. Pat. No. 4,234,435 (Col. 42, lines 33-46).
The use of isophthalic and terephthalic acids as corrosion-inibitors is described in U.S. Pat. No. 2,809,160. The corrosion-inhibitors are used in combination with detergent additives.
The preparation of lubricating oils containing ashless dispersants obtained by reaction of aliphatic and aromatic polycarboxylic acids with acylated amines have been described previously. For example, U.S. Pat. No. 4,234,435 describes lubricating oils containing carboxylic acid derivative compositions prepared by post-treating acylated amines with a variety of compositions including carboxylic acid acylating agents such as terephthalic acid and maleic acid. U.S. Pat. No. 3,287,271 and French Pat. No. 1,367,939 describe detergent-corrosion inhibitors for lubricating oils prepared by combining a polyamine with a high molecular weight succinic anhydride and thereafter contacting the resulting product with an aromatic dicarboxylic acid of from 8 to 14 carbon atoms wherein the carboxyl groups are bonded to annular carbon atoms separated by at least one annular carbon atom. Illustrative of such aromatic dicarboxylic acids are isophthalic acid, terephthalic acid and various derivatives thereof. Lubricating compositions containing amine salts of a phthalic acid are described in U.S. Pat. No. 2,900,339. The amine salts are thermally unstable salts of the phthalic acid and a basic tertiary amine. U.S. Pat. No. 3,692,681 describes dispersions of phthalic acid in hydrocarbon media containing highly hindered acylated alkylene polyamines. The polyamines are prepared by reaction of an alkenyl succinic anhydride with an alkylene polyamine such as ethylene polyamine or propylene polyamine. The terephthalic acid or its derivative is dissolved in an auxiliary solvent such as a tertiary alcohol or DMSO, and a terephthalic acid solution is combined with a hydrocarbon solution containing the hindered acylated amine address detergent. The auxiliary solvent then is removed.
U.S. Pat. No. 3,216,936 describes lubricant additives which are compositions derived from the acylation of alkylene polyamines. More specifically, the compositions are obtained by reaction of an alkylene amine with an acidic mixture consisting of a hydrocarbon-substituted succinic acid having at least about 50 aliphatic carbon atoms in the hydrocarbon group and an aliphatic monocarboxylic acid, and thereafter removing the water formed by the reaction. The ratio of equivalents of said succinic acid to the mono-carboxylic acid in the acidic mixture is from about 1:0.1 to about 1:1. The aliphatic mono-carboxylic acids contemplated for use include saturated and unsaturated acids such as acetic acid, dodecanoic acid, oleic acid, naphthenic acid, formic acid, etc. Acids having 12 or more aliphatic carbon atoms, particularly stearic acid and oleic acid, are especially useful. The products described in the '936 patent also are useful in oil-fuel mixtures for two-cycle internal combustion engines.
British Pat. No. 1,162,436 describes ashless dispersants useful in lubricating compositions and fuels. The compositions are prepared by reacting certain specified alkenyl substituted succinimides or succinic amides with a hydrocarbon-substituted succinic acid or anhydride. The arithmatic mean of the chain lengths of the two hydrocarbon substituents is greater than 50 carbon atoms. Formamides of monoalkenyl succinimides are described in U.S. Pat. No. 3,185,704. The formamides are reported to be useful as additives in lubricating oils and fuels.
U.S. Pat. Nos. 3,639,242 and 3,708,522 describe compositions prepared by post-treating mono- and polycarboxylic acid esters with mono- or polycarboxylic acid acylating agents. The compositions thus obtained are reported to be useful as dispersants in lubricants and fuels.